As far as I'm concerned, the premier Indy reference site is still Greg Douglas' Indytech at Reputable.com:

Greg Douglas wrote:The MIPS R4600 CPU was redesigned using a smaller geometry, and a 3.3 V process, which means much less heat dissipation. The 4400-175, and 200 MHz. also use the 3.3V process, but still have a porcupine heatsink.

recondas wrote:As far as I'm concerned, the premier Indy reference site is still Greg Douglas' Indytech at Reputable.com

...which reminds me: some of you may have noticed that Greg is looking to sell the Reputable.com domain. I asked him if he wouldn't mind if someone hosted an archive copy of his site, including Indytech, etc.

As far as I'm concerned, the premier Indy reference site is still Greg Douglas' Indytech at Reputable.com:

Greg Douglas wrote:The MIPS R4600 CPU was redesigned using a smaller geometry, and a 3.3 V process, which means much less heat dissipation. The 4400-175, and 200 MHz. also use the 3.3V process, but still have a porcupine heatsink.http://www.reputable.com/indytech.html#CPUmodule

Ok... great, does this means that a R4400 200Mhz module (cpu + the module/board is sits in) drops right in? I just have to check PROM version...

Out of interest, is it the motherboard that supplies the 3.3v or is it the CPU module/board that this CPU sits in that generates the 3.3v?

I haven't had an indy in a number of years, so don't act on my recollections without some independent verification. I did an upgrade from an R4600 CPU to an R5000 that was a straightforward CPU/PROM swap.

So as far as I remember, you can physically swap one *indy* CPU for another. One of the larger gotchas of the day was that newer CPUs frequently required a newer PROM revision, which usually meant sourcing a new PROM chip along with the CPU. The Indy page at sgistuff.net mentions that you'll need a PROM with a revision date of July 15, 1994 or later to use a 200MHz R4400 in your Indy.

cris_adder wrote:Ok... great, does this means that a R4400 200Mhz module (cpu + the module/board is sits in) drops right in? I just have to check PROM version...

Out of interest, is it the motherboard that supplies the 3.3v or is it the CPU module/board that this CPU sits in that generates the 3.3v?

Thanks....

Indy modules are interchangeable, and if you've got a R4600 it's likely that you have a sufficiently new PROM for the R4400. In many cases, the only issue with a too-old PROM for the specific speed of a processor is that the PROM "hinv" will misreport (note that this isn't true for type of processor. R4600, R5000, etc. all need PROMs that support them).

For most instances the CPU board provides the +3.3V. Some of the faster 180MHz R5000 boards had a DC-DC section, I'm not sure why. Probably the R5k/180+cache was a little too close to the limit for comfort. (most R5k/150s don't have the converter).

cris_adder wrote:Just wanted to ask if the Indy R4600 CPU a 3.3v or 5v CPU?[...]Have seen a few posts on this board and on Google that say both 3.3v and 5v. So just wanted to clear this up...

Was thinking about swapping in an R4400 200Mhz in one of my Indy's but wanted to confirm the voltage first (as the 200Mhz is 3.3v).

Thanks...

Sorry for reopening this old thread, but I stumbled upon it during a search for a more or less similar question.

I want to use a R4700 in an Indy and assumed that these are 3.3 V only as they followed the R4600, from which the Indytech mirror says: "[...] The MIPS R4600 CPU was redesigned using a smaller geometry, and a 3.3 V process [...]". But I there (and also on the forum) I saw that there were/are different versions of the R4600 based CPU modules for the Indy available, (1) one with a smaller heatsink glued to the CPU and (2) one with a bigger porcupine heatsink (similar to the R4400 heatsinks) attached via a clamp (like mine!).

Reading the data sheet of the R4600 it looks like there were indeed two voltage versions manufactured. The 5 V version is called R4600 and the 3.3 V version is called RV4600 - when ordered. I don't know if they also have a different name printed on the heat spreader and I also couldn't find a picture of an RV4600 online to check, but the CPU in my R4600SC board (for an Indy) has "R4600" printed on the heat spreader.

Trying my R4700 with "R4700" printed on the heatsink in this R4600SC board indeed worked long enough to start the POST. It later crashes with an exception, but I assume this could be either due to my PROM version or the lower speed the R4700 was meant for (100 MHz instead of 133 MHz). I don't believe it's a voltage issue. The R4700 data sheet (sorry, cannot link as there are brackets in the URL, search the WWW for "idt79RV4700_DS_5622[1].pdf") makes a similar statement as the R4600 data sheet: R4700 for 5 V and RV4700 for 3.3 V. And on Ebay I could indeed find some pictures of RV4700 CPUs. Hence I'd say both my CPUs use the same voltage and are 5 V versions.

cris_adder wrote:Does this voltage come from the motherboard of the CPU board?

As I don't see any voltage regulators between the power header on the motherboard and the connector for the CPU module and also no obvious voltage regulators on my CPU boards (I have a R4600SC 133 Mhz and a R4400SC 175 MHz (the latter with "3.3 V" printed on the PCB)), I think power comes directly from the PSU, most likely both for 5 V and 3.3 V and the CPU is fed by the rail that is actually used by the CPU module. Or that the connectors of the CPU module both use 5 V and 3.3 V and route the respective rail to the CPU. This would imply that both versions of the R4600 CPU modules (small heatsink/big heatsink) route different voltage rails to their CPUs. But I cannot verify this currently, as I only have one R4600 CPU module with big heatsink and assumed R4600 CPU using 5 V.

The gold pads on top of the ceramic PGA package are for bypass capacitors, which are each across Vdd and Vss. You should be able to measure the voltage of the CPU's power rails on those pads (but be careful you don't slip a probe, I don't think the results will be pretty if you accidentally short 5V to 3V3). There may be pads for multiple rails, or only one.

robespierre wrote:The gold pads on top of the ceramic PGA package are for bypass capacitors, which are each across Vdd and Vss.

I don't think I can get to the pads when it's running with the heatsink on top and I am afraid to let it run without (even for a short amount of time). But I could try to follow the 5V and 3.3V rails from the PSU to the CPU socket (although there are 160 pins (J500, J501 on the CPU module) to check, Pin 1 on J500 is 3.3V if I didn't make an error).